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Recurrent miscarriages: testing for the causes

by Dr Lizle Oosthuizen
Baby Yum Yum - Recurrent miscarriages testing for the causes
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Any pregnancy loss is a devastating, scary and lonely experience. While miscarriages are very common, every woman who experiences this kind of loss is concerned about her chances of a successful pregnancy the next time she conceives.

The reassuring news is that less than 3% of women will experience more than one miscarriage in her reproductive life, but that second loss can leave you with more questions and fears.

What counts as recurrent pregnancy loss?

We used to define this as three consecutive pregnancy losses. Recently we have changed our definition to two pregnancy losses, whether consecutive or not. This is mainly because we have discovered the tests we can offer are not more or less likely to be positive after two or three losses.

What tests look for

1. Genetics

We can divide tests into two groups – those that look for an explanation for this pregnancy loss, and those that try to find an underlying cause.

The majority of pregnancy losses are due to a chromosomal (genetic) abnormality in the pregnancy. Around half of all miscarriages can be explained by this. The good news is that most of these are sporadic events and are not likely to repeat. From a genetic point for view, we can offer two tests.

  1. We can test the pregnancy tissue for the genetic make-up. If we find an abnormality it gives us some closure about why the pregnancy failed. It does however require obtaining a sample of the pregnancy tissue for testing, and this is most often done at the time of a surgical evacuation of the uterus (womb scrape). It also does not rule out other causes of recurrent pregnancy loss – it’s possible that this pregnancy happened to be abnormal, but there still can be another underlying issue. If the result is normal, we still don’t know if there was something developmentally wrong with the pregnancy (e.g. the heart didn’t form properly/ the brain didn’t develop as it should).
  2. Your and your partner’s genetics, called a karyotype, can be tested. This is not usually a routine test, as it is both expensive and unfortunately only finds a problem in about 2% of couples. While a problem in your genetic make-up is an important thing to diagnose, most genetic problems still only pass on to 1:4 to 1:2 children, so the chances of a subsequent healthy baby is still good. You can chat to your doctor about the treatment options available if a genetic abnormality is detected. We might be more likely to do this test if there is a family history of abnormalities, you have had a previous pregnancy born with abnormalities, or started suffering miscarriages after a healthy first pregnancy.

2. Clotting issues

The next batch of tests are usually aimed at clotting issues. While inherited clotting issues have received a lot of attention, we don’t have much evidence that they cause miscarriages, or that treatment helps.

Your doctor will likely only test this if you have a family history of clotting issues, or have had a clotting problem yourself before.

The one exception to this is called Antiphospholipid Syndrome (APLS). This is an acquired condition (you are not born with it).. Your doctor can check for the APLS antibodies in your blood. They can also only be done six weeks after any pregnancy, as pregnancy can raise the levels.

If they are positive, we have to repeat the test 12 weeks later, as they can sometimes fluctuate. We do have some evidence for treating this with a combination of Aspirin and blood thinning injections. Most guidelines still only recommend treating after three losses though, as a blood thinner can have serious side effects.

Recurrent pregnancy loss

3. Hormone levels

The thyroid has been a very controversial area of study with recurrent miscarriages. Your doctor should test to make sure there is no thyroid problem, and they may test the antibodies to the thyroid hormones.

While we know that overt thyroid disease can be linked to worse pregnancy outcomes and should be tested, the difficulty comes in when your brain has to make higher levels of thyroid stimulating hormones (TSH) in order to get the thyroid to respond. We call this subclinical hypothyroidism, where the end result is normal levels of circulating hormones, but higher than usual TSH levels.

Every society has a different view on this, but most doctors would elect to treat you if you have convincing subclinical hypothyroidism. If only the antibodies are positive, we now know that low doses of thyroid hormones are not effective at preventing miscarriages. So why test you ask? We test because you may be at higher risk of developing a thyroid problem in pregnancy, and this way we will know to monitor you more closely.

Some women may ask about progesterone levels in the pregnancy. There is a lot of dispute whether a “short luteal phase” is actually a real thing – and there is no way to test this to be sure. Progesterone is a bit of a chicken or the egg issue, as it is secreted from the little follicle that ovulates the egg to maintain pregnancy.

If we test it and it is low, is it the low progesterone causing the miscarriage, or the fact that it’s an abnormal pregnancy causing the low progesterone? We do know from a big study in women who fell pregnant and started progesterone that it did not reduce the miscarriage rates.

We also know from another big study that women with bleeding in pregnancy are unlikely to benefit from progesterone unless they have had 3 or more miscarriages. Progesterone is quite cheap, has very little side effects, and is generally considered safe to use. Therefore, your doctor may decide to prescribe it. It’s not, however, the answer to every problem.

4. The uterus

Your doctor will have a good look at the inside of the uterus on scan, called the endometrial cavity. We look for growths such as polyps (little glandular outgrows from the lining), fibroids (muscular growths of the muscle of the uterus), or scar tissue.

We don’t have the evidence to say these problems cause miscarriages, and there is also the risk that surgery may leave some scar tissue. It’s important to chat to your doctor about these findings, as we can run through the pros and con’s of surgery with you.

We may want to do a hysteroscopy, a procedure where we look inside of the womb to look for scar tissue and remove it, but this may require more than one procedure to make sure there is a good result and no scaring afterwards.

Sometimes we may discover an unusual shape to the uterus, such as a septum. We used to routinely operate on these developmental abnormalities, but the evidence is starting to show that we need to think twice, as it does not always result in a better outcome, and it can leave scar tissue behind.

If the miscarriages are happening in the second trimester, we may consider the cervix being weak. This usually has a history of painless dilating of the mouth of the womb, that may result in bleeding and is followed by the loss of the pregnancy. We can monitor the length of the cervix after 12 weeks, and your doctor may consider placing a stitch to strengthen the cervix or starting some progesterone gels to relax the uterus.

How to test for miscarriage issues

So where does this leave us?

The reality is that on the whole, the group of women who suffer from repeat miscarriages can have a variety of causes, and half of the time we won’t find a cause. If we do find a cause, we can’t always treat it.

The most important factors to consider are your age and how many miscarriages you have had, but the chances of a successful pregnancy are still good! While we may not always be able to offer a treatment, we can make sure we detect pregnancy early, we can monitor the pregnancy closely and provide support in this very anxious time.

We understand the “not knowing” if everything is still okay is emotionally exhausting, and the fear can be debilitating.

While we might not be able to change anything where a cause is not found, we can support you and your family through this and make sure you have the extra access to a doctor when you need it, even if it’s just for reassurance.

About Dr Lizle Oosthuizen

Dr Lizle Oosthuizen is a registered specialist obstetrician and gynaecologist practising at Cape Fertility in Claremont Cape Town as a fellow in Reproductive Medicine. She completed her undergraduate studies at the University of Cape Town in 2007. In 2010 she started work at a rural Eastern Cape hospital and headed the only unit in the province to have no maternal mortalities. 

After obtaining certificates in abdominal and gynaecological ultrasound, she returned to complete her specialist degree in Obstetrics and Gynaecology at the University of Cape Town in 2015. Her interest in Reproductive Medicine and Endocrinology culminated in a Masters degree focusing on the effects of lifestyle factors on male fertility.  

Dr Oosthuizen is part of the fellowship program in Reproductive Medicine at the University of Cape Town. 

She has previously practised for a year in Port Elizabeth as a general Obstetrician and Gynaecologist at Netcare Greenacres Hospital prior to joining Cape Fertility in 2017. Her special interests include fertility, endocrinology, and recurrent pregnancy loss. When not working in her busy practise, she enjoys photography, music and travel. 

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